Don't know how to factor this - Math Help Forum

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#1

$Old$ November 10th, 2008, 06:13 AM

Alienis Back $Alienis Back is offline$

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$Default$ Don't know how to factor this

Just give me some guidelines. I don't want you to give me the answer unless it is necesary so I can understand.

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$Old$ November 10th, 2008, 06:22 AM

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You can go a little further. What you have is a difference of 2 cubes:
$(a^3 - b^3) = (a-b)(a^2+ab+b^2)$

In the future, if you run into a sum of 2 cubes:
$(a^3+b^3)=(a+b)(a^2-ab+b^2)$

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$Old$ November 10th, 2008, 06:27 AM

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Quote:

Originally Posted by Alienis Back $View Post$

Just give me some guidelines. I don't want you to give me the answer unless it is necesary so I can understand.

1. All your considerations and calculations are OK.

2. Use the property: $x^3-1=(x-1)(x^2+x+1)$

3. Keep in mind that $8a^3 = \left(2a\right)^3$

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